FAQ on the Apple iPad’s IPS display

So Apple let the tablet out of the bag and showed off its new iPad this week. With all the hoopla of a presidential inauguration, the covers were pulled back to reveal…a fairly modest tablet computer.

Nothing from the iPad specs that I’ve seen really shows any great cause for celebration. It looks like a nice product, but it’s not exactly earth-shattering. The one thing that was surprising was the inclusion of an IPS display. Having spent the last couple weeks deep in the darkness of the GCN Lab (and this time it really was dark) testing LCDs for our 2010 LCD roundup, I’m in a unique position to explain what that means. And because several readers have written in already to ask, I figured it was a good topic to cover.

IPS stands for In-Plane Switching Display. It’s one of the newer innovations that we’ve found in looking at LCDs for the roundup review. Although some companies have moved to using LEDs to power the backlight, others have stuck with normal fluorescent tubing but improved their LCD is different ways, like going with IPS. The ViewSonic VP2365wb is an example of an LCD that uses IPS.

Most LCD screens today use TFT, which is a thin film transistor liquid crystal display. However, having tested both TFT and IPS, I can tell you that IPS offers far superior image quality and color matching. IPS works because it aligns each tiny liquid crystal horizontally, which covers more of the screen and offers better coverage, as well as much better viewing angles. How it does this is by applying an electrical field to both ends of each crystal, causing them to stretch out.

For an LCD monitor like the VP2365wb, it works great, enabling the $399 unit to compete with much more expensive LED-backlit displays. However, there are drawbacks to IPS, which make me wonder why Apple would put it in the iPad. The first is that TFT displays require only one transistor, which twists the crystal to create an image. With IPS, you need two transistors for every single pixel, one for each end. Right there you are doubling the power consumption of your monitor. But it goes beyond that. Because more of the surface area of the screen is “covered” by images, it also means you need a much more powerful backlight to shine through. And that means either more florescent tubes or much brighter ones. Either way, you are talking about more power.

I’ve been covering and reviewing notebooks and battery technology for the past decade, and I know what the current technology is capable of. There is no way that a 1.5-pound computer is going to be able to drive an IPS display for ten hours as Steve Jobs claims. It just can’t happen. Perhaps if you let the iPad lapse into standby mode, you could squeeze it. But if you are actually using the device, my estimate would be less than three hours of power, and that’s being generous. The display would look amazing, but be quite a power hog.

Unless Apple has also developed some new type of power source, such as nuclear cells or magical hamsters on tiny spinning wheels for the iPad, don’t expect the claims about battery life to hold true. The candle that blazes the brightest is always the first to go out.